Nickel base alloys of improved properties

ABSTRACT

A yttrium addition, which may be made in the normal course of vacuum melting, is employed to improve high temperature properties and hot workability of nickel base alloys.

United States Patent 1191 Kennedy Sept. 23, 1975 [5 NICKEL BASE ALLOYS 0F IMPROVED [56] References Cited PRQPERTIES UNITED STATES PATENTS [75] Inventor: R chard L. Ke y, Monroe, NC. 3,399,058 8/1968 Roush 75/171 3,575,734 4/1971 Muzyka et a1. 75/171 [73] Asslgwe' Teledyne L05 Angeles 3,754,902 8/1973 Boone et a1 75/171 [22] Filed: Mar. 16, 1973 Primary Examiner-R. Dean 21 A 1. N 342074 1 pp 0 Attorney, Agent, or Firm-Richards, Shefte &

Related US. Application Data pi k [63] Continuation-impart of Ser. No. 188,260, Oct. 12,

1971, abandoned. [57] ABSTRACT 52 US. (:1. 75/122; 75/134 F; 75/170; A yttrium addition, which y be made in the normal 1 75 7 course of vacuum melting, is employed to improve 51 1111.01. C221: 19/00 high temperature Properties and her workability of [58] Field of Search 75/171, 170, 122, 134 F; niekel base y 14 Claims, 2 Drawing Figures 05% Magnesium added No addition .Ol% Yttrium added .05% Yttrium added Degree of cracking experienced on forging US Patent Sept. 23,1975 3,907,552

- .O5% Magnesium added No addition .O|% Yflrium added 05% Yttrium added .O5% Magnesium added No addition .O|% Yttrium added .05 Yflrium added Fig 1 Degree of edge cracking experienced on rolling iniiiiii NICKEL BASE ALLOYS OF IMPROVED PROPERTIES CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of copending application Ser. No. 188,260, filed Oct. 12, 1971, and now abandoned.

BACKGROUND OF THE INVENTION It is generally well known by those familiar with the manufacture of nickel base alloys that the addition of extremely small quantities of certain elements can have pronounced effects on their properties. The elements boron and zirconium, for example, have been known for years to improve significantly the creep properties of many nickel base alloys, although these elements are not usually credited with improving workability.

Recently, magnesium has been recognized as improving both the elevated temperature properties and hot workability of this class of alloy (see US. Pat. No.

3,512,963 and No. 3,575,734). The addition of Mg to the nickel base alloys is quite difficult, however, since most of them are usually vacuum melted. Because of its low melting point and high vapor pressure at the melting temperature of these alloys, the amount of Mg retained in the cast product may be quite low in comparison to the amount added, frequently 50 per cent or less. The addition must therefore usually be made under a partial pressure of an inert gas to aid in retaining the highest possible percentage of the amount added. Even then, depending upon pressure, temperature, and time, the amount of Mg retained often varies to a degree which causes significant variations in workability and properties from heat to heat and between different ingots cast from the same master heat.

Further problems may occur due to the presence of a Mg addition in consumable vacuum arc remelting, which is the highly desirable second step of the double melting process in which an intermediate ingot cast in the first melting operation, commonly called an electrode, is consumably remelted under vacuum in a water-cooled copper crucible. Typically, additional Mg is lost in this operation. In order to retain a significant amount of Mg, it is again necessary to remelt under a partial pressure of an inert gas, such as argon or helium, which has a detrimental effect on ingot surface quality and resulting product yield.

A principal object of the present invention was to develop a method for improving the hot workability'and elevated temperature properties of nickel base alloys,

Alloy C Cr Mo Co 901 .05 12.5 5.7 625 .05 21.5 9.0 11 1-102 .06 15.0 3.0 [NOR-8 .06 7.0 16.8

HastX .10 22.0 9.0 1.5 HastB .03 28.0 Hast c .04 15.5 16.0 HastW .06 5.0 24.5 llliumR .05 22.0 5.0 Illium 9s .04 28.0 8.3 ,Rene4l .012 19.0 9.8 11.0

. 2 and to obtain. such alloys of improved nature in these respects. It was a further object to providea process for accomplishing this result which is more compatible with the vacuum melting operations commonly employed on nickel base alloys.

It has been discovered that all of these objectives can be met by the addition of small amounts of yttrium (i.e., in the range from about 0.02 to about 0.15 weight per cent). Yttrium has been added as an alloying element to various hightemperature alloys in the past (see, for example, U.S. Pat. No. 3,516,826, No. 3,346,378 and No. 3,202,506). The principal reason for its addition, however, has been to improve the resistance of the resulting alloy to corrosion at high temperature from 0 N S, V, Pb, etc. In general, the amount of yttrium usually added for this reason is considerably larger (up to 3 per cent) than that required or desirable in the present invention.

The beneficial effects of yttrium additions on hot workability and elevated temperature stress rupture properties have not been recognized before. The probable reason for this is that at the high concentrations heretofore used there is often a detrimental effect on both hot workability and elevated temperature mechanical properties.

SUMMARY OF THE INVENTION Basically, the method of the, present invention involves vacuum melting a nickel base alloy in the usual manner. After the refining action of the vacuum treatment has been completed, the yttrium addition is made to the molten metal under vacuum conditions (i.e., less than 50 X 10 mm Hg). Yttrium may be added in pure (elemental) form or by means of a yttrium-bearing material, such as a master alloy (e.g., YzCr) or a commer cial grade of yttrium in which certain rare earth metals remain admixed. The yttrium addition is delayed until late in the melt cycle because of its very great reactivity. This permits many of the contaminates with which yttrium might react to be removed prior to its addition, thus effectively reducing the amount required and also limiting the amount of time available for any adverse reaction between the melting crucible material and the yttrium. The advantages achieved according to the present invention by the addition of yttrium can also be obtained by introducing it in the course of air melting procedures for any nickel base alloys that are otherwise suited to air melting.

Nominal compositions of typical nickel base alloys which can be treated advantageously in accordance with this invention are given in Table I that follows.

TABLE I Ti Al Fe Ni Cb Other 0.9 0.5 18.5 Bal.* 5.2 2.5 0.8 6.8 Bal.* 1.0 1.8 0.2 Bal.* 41.5 2.9 2.8 0.2 Balf 42.5 0.2 0.2 2.5 Bal.* 4.0

.6 .4 7.0 Bal.* 3.0 3.0 W

2.5 Bal.* 18.5 Bal.* 0.6 W 5.5 Bal.* 0.4 V 5.5 Bal.* 3.8 W 5.5 Bal.* .30 V 6.0 Bal.* 2.5 Cu

' Bal.* 5.3 Cu 3.2 1.5 Bal.*

Bal Balance essentially, including minor amounts of impurities and any or all of Mn, Si, B and Zr As illustrated by the foregoing tabulation, and as furdata set forth below, the nickel base alloys subject to effective treatmentaccording to the present invention alloy with a composition of about 0.03% carbon, 18.8% chromium," 3.'l% molybdenum, 0.9% titanium, 0.5% aluminum, 18.0% iron, 5.0% columbium, balance essentially nickel. Each of the heats was melted and re- The following examples will serve to illustrate the sig-v EXAMPLE 1 e A series of 45-pound double vacuum melted ingots were prepared from a master melt of an age-hardenable are those' in which cobalt, if present, does not exceed 5 fined in vacuum in the normal manner. The first elecabout 12 per cent, inwhich chromium, if present, does trode in the series (D871 was cast at a pressure of 20 not exceed about 28 per cent, andin which titanium X mm Hg with no special additions. For the replus aluminum, if either or both is present, does not exmaining heats (D872-7), the melt chamber was backceed about 5 per cent, all by weight. Beyond these lirripressured with argon to about 80 mm Hg, following the its it is not possible to predict the effect of a yttrium ad refining cycle and just prior to casting, and an addition dition from data presently availablefand as additions of yttrium (pure) or magnesium (as MgzNi master alexceeding any of these limits materially is apt to introloy) was made inthe amount shown in Table II. All duce special conditions of .uncertain effect, it is to electrodes in this series were consumably arc remelted nickel base alloys of the familiar sort falling within the to 4 inch diameter ingots. The one formed from the foregoing limits and as illustrated by the foregoing tabheat with no special additions (D871) was remelted in ula'tion'that the present invention is directed. a vacuum of 6 X 10' mm Hg. The remaining elec- The improvement obtained by the addition of yttrium trodes were remelted under an argon partial pressure of varies with the type of alloy involved and with the 40 mm Hg in order to maintaina constant ingot surface amount of yttrium added. In the case of age-hardenable condition. The pressure used on consumable remelting alloys the notable improvement is in high temperature is not considered to be a factor in mechanical properor mechanical properties, as these alloys as a class hot ties, however, because'of the small ingot size involved. work quite well if adequate temperature control is The resulting ingots were rolled to /1 inch square bar maintained. Those alloys that are not age-hardenable, using identical procedures in each case. The hot rolled however, have very poor hot workability asa class,'and bar was solution treated for 1 hour at 1,750F., folit'is in this respect that significant improvement is oblowed by air cooling and aging for 8 hours atl,325F., tained with such alloys. and then by furnace cooling at 100F. per hour to As to the addition amount, the data that follow show 1,150F., holding for an additional 8 hours, and air effects through a yttrium addition range from about cooling. Upon completion of stress rupture testing at 0.02 to about 0.15 weight per cent, as mentioned ear- 1,200F. and 1 10,000 psi, it was apparentas set forth in lier, and indicate disadvantage or at least lack of bene- Table II that the alloys treated with yttrium additions fit above or below this range. The data further indicate had rupture ductilities significantly in excess of those of a preferable range from about 0.05 to about 0.075 the alloy with no additions. It was further observed that weight per cent yttrium. the yttrium treated alloys exhibited rupture ductilities i full com ar ble to those of the ma nesium treated al- DESCRIPTION OF THE DRAWINGS loysy p a g Y TABLE 11 I Reduction Heat Special Addition, Rupture Elongation in Area Test No. Weight Percent Life Hours Percent Percent Bar D871 None 67.4 10.5 v 19.5 CSN 93.0- 12.5 25.0 CSN D872 0.025 yttrium 47.6 21.9 35.9 1 g 54.2 22.2 34.7 D873 0.050 yttrium 52. 8 30.9 59.6 97.1 23.6 60.6

D874 0.075 yttrium 81.0 30.1 "59.8 1 g 115.0 27.6 63.9 D875 0.100 yttrium 35.1 36.5 59.8 39.7 25.7 60.5 D876 0.100 magnesium 88.9 32.7 56.2 103.8 26.4 58.3 D877 0.150 magnesium 144.7 33.l 50.9 87.6 18.4 44.1

CSN Combination smooth and notch test bar.

FIG. 1 consists of photographic illustrations of the degree of cracking experienced in forging'with the various additions noted; and

FIG. 2 is a comparable illustration of the degree of EXAMPLE n edge cracking experienced in rolling. e e

' It is well known in the industry'that the alloy used in DETAILED DESCRIPTION OF THE INVENTION Example I is subject to notch embrittlement under certain conditions of forging or heat treatment. To proand 1 10,000. psi with the results set'forth in the following Table III. I v

TABLE III Heat S pecial Addition, Rupture Elongation RA Test No. Weight Percent Life Hours Percent Percent Bar D871 None 1.1 N. B.* CSN 1.1 N.B.* CSN D872 0.025 yttrium 4.5 N.B.* CSN 77.5 4.9 12.2 CSN D873 0.050 yttrium 158.9 7.3 13.1 CSN 122.7 9.3 15.3 CSN D874 0.075 yttrium 79.9 5.1 10.0 CSN 36.5 8.1 7.8 CSN D876 0.100 magnesium 93.4 7.7 13.2 CSN 105.3 4.7" 9.9" CSN D877 0.150 magnesium 103.2 3.9" 10.8" CSN 13.1 8.7" i 7.8 CSN N8. notch break Broke outside of punch mark. Broke within one diameter of punch mark. CSN Combination smooth and notch bar.

It is to be noted that the heat with no addition was se- TABLE IV-Continued verely notch embrittled by the foregoing heat treat- Hem Special Addition, Hot ment, failing in the notch after only 1.1 hours, while Percent workability those heats containing yttrium additions resisted notch D3474 (105% yttrium Good embrittlement and failed in the smooth section of the test bar in all cases but'one.

EXAMPLE m A series of 12-pound ingots were prepared from a master melt of ah alloy containing about 0.04% carbon, 21.0% chromium, 8.6% molybdenum, 0.10% aluminum, 2.5% iron, 3.7% columbium, balance essentially nickel. Each of the ingots was melted and refined in vacuum in the normal manner, with two ingots being cast sequentially from each of two 24-pound furnace charges. At the end of the normal refine cycle and just before pouring, an addition of 0.05 magnesium was made under an argon back pressure of 250 mm Hg to the molten metal in the first furnace charge. The first l2-pound ingot from this charge was then cast at this same pressure (D344-l The furnace was evacuated again and the remaining molten metal of the charge was held for one hour under a vacuum of less than 50 X 10" mm Hg to effect complete removal of the initial magnesium added by means of vaporization. The second l2-pound ingot, considered to be magnesium free, was then cast (D344 -2) at a pressure of 15 10 mm Hg. Yttrium additions were made to the second furnace 1 charge and ingots cast sequentially to produce levels of All of the ingots were hot worked fromnominal 2 inch square tapered ingot size to X 1 [2 inch flat bar by forging and rolling. The same procedures were used on each. Hot workability of the heat to which 0.05% yttrium had been added (D347-2) was very good and essentially the same as that of the heat to which 0.05 Mg had been added (D3444 workability of the heat with a 0.01% yttrium addition (D347-1) was poor but wassignificantly better than the heat to which magnesium had been added and then removed by holding under vacuum (D344-2)L These ,results can be seen from FIGS. I and II and Table IV.

TABLE IV Hem Special Addition, Hot

No. Percent workability 0344-1 0.05% magnesium Good D344-2 Very Poor 0347-1 0.01% yttrium Poor Elevated temperature tensile testing was conducted as another measure of hot workability on bars cut from the heat having the 0.05% yttrium addition (D347-2). Reduction in area is generally regarded as an indication of hot workability according to this test. The results on this heat confirmed the good workability observed in rolling with values of to 99% reduction in area over the temperature range of 2,200 to 1,700F. At 2,150F. the reduction in area of 92.4% compared very favorably with the resultfrom the heat with the 0.05% magnesium addition which was 88.5%. Previous tests on other heats of this alloy with proven poor workability had a maximum value over this same temperature range of 60% reduction in area.

As an additional check on this experiment, a 45- pound heat of essentially this same composition (Heat No. D407) was melted from virgin raw materials. After vacuum refining in the normal manner and adding the usual late additions, 0.05% yttrium was added under a vacuum of 12 X 10 mm of Hg and the heat was poured. The resulting electrode was vacuum are remelted at 3 X 10 mm of Hg to produce a 4 inch diameter ingot which was subsequently rolled to 0.440 inch diameter bar. workability was rated as good based on actual mill observation, and by virtue of the fact that the small diameter bar was rolled essentially crack free. Elevated temperature tensile tests resulted in values of reduction in area ranging from 99.0% at 1,700F. to 72.3% at 2,100F. Although slightly lower than results on the l2-pound ingots, these values are still significantly above the 60% reduction in area maximum values'experienced on the heats with extremely poor hot workability.

EXAMPLE IV A 8 rolling experience. Similar data collected on a good working heat with'a magnesium addition ranged from 97.8 to 81.2%, while data from a heat with extremely poor workability showed a maximum value of reduction in area. From these data it is apparent that the 7 addition of yttrium produced a significant improvement in the hot workability of this group of alloys.

EXAMPLE Vl TABLE V Reduc- Test Elontion Heat Special Addition, Temp. Stress Rupture gation in Area No. Weight Percent (F.) Ksi Life Hrs. Percent Percent G049 None 1350 45/55" 703/7505 3.2 7.7 1350 45/55" 703/7349 3.5 9.3 1350 60 158.0 7.9 7.7 G052 0.050 yttrium 1350 45/55 703/8637 6.9 21.6 1350 45/55" 703/7475" 81 22.3 1350 60 241.0 13.6 22.4

"Stress increased from 45 m 55 Ksi at 703 hours on each bar. I

EXAMPLE v A group of solution hardened alloys were prepared with compositions as shown in Table VI below.

A series of 47-pound doublevacuum melted heats were made of an age-hardening alloy with a composition of about 0.03% carbon, 15.2% chromium, 41.5% nickel, 2.8% columbium, 1.6% titanium, 0.25% aluminum, 0.005% boron and balance essentially iron. Each heat was prepared from a master melt of this same alloy in order to keep the base chemistry as consistent as p0ssib1e. A1l the heats were vacu'um melted and refined in-the normal manner with the exception of Heat G081 TABLE VI Heat Y added No. by Wt.) C Cr Mo Co Fe Ni Other D422 .05 .01 5.8 24.1 .7 5.7 Bal.* .12V D432 I .05 .10 21.4 8.9 2.3 19.0 Bal.* D454 7 .05 .03 0.3 26.3 .2 5.5 Bal.* .3V D455 .05 .05 13.0 17.1 6.8

"" essentially, minor Based on actual production experience, it is well known that the hot workability of all of these alloys is very poor unless they contain some special addition such as magnesium. Each of these alloys was melted and refined in vacuum in the usual manner. Yttriumadditions of 0.05% were made to the molten charge shortly before casting in each caseat vacuum levels of 3'to 12 X 10 mm Hg. Electrodes from Heats'D422, D454 and D455 were then vacuum arc remelted to 4 inch diameter ingots at vacuum levels of 2 to 8 X 10 mm Hg. Heat D432 was prepared as a 4 inch square static cast ingot from the initial vacuum induction melt, and remelting was not performed on it. Each of these ingots was hot worked by rolling in a manner typical for that alloy. An initial breakdown'operation was performed after which light grinding was required on each ingot except D432 to remove minor defects typical of those resulting from the as-cast ingot surface. No conditioning was required -on the static cast ingot (Heat D432). Followingthis operation, bar product was rolled from each heat with no evidence of cracking. Hot workability was judged excellent in all cases.

Elevated temperature tensile testing was performed on bar rolled from Heat D455 over the temperature range of l,700 to 2,200F. Reduction in area, considered to be a rough measure of hot workability, ranged from 96.4 to 98.4% over this entire temperature spread, correlating very well with the favorable bar of impurities and any or all of Mn, Si, B. Zr.

to which a special sulfur reducing slag was added. Yttrium additions were made under full vacuum just prior to pouring to selected heats as shown in Table Vll. A magnesium addition was made to Heat G169, also just prior to pouring, but under a partial pressure of argon gas. Commercially avilable forms of yttrium of and 99 per cent purities were employed. The magnesium addition was made as a Ni-Mg master alloy. All electrodes were vacuum arc remelted into 4 inch diameter ingots. The control heats,-those to which no additions had been made, and the yttrium containing'heats were remelted under full vacuum, although the pressure varied slightly as shown in Table VII. The magnesium containing heat was remelted under an argon partial pressure of mm Hg. All other melting conditions were identical. I

Since the alloy employed in this experiment is used in some cases as a casting alloy, testing was performed on samples sectioned directly from the as-cast ingots Test barsv were machinedfrom the same, position from each of theingots prepared. These samples were heat treated by heating to 2,000F. for 1 hour followed by 9 90,000 psi. The results of this testing, as summarized in Table Vlll, show a significant improvement in stress rupture ductility for heats with yttrium additions of 0.05 and 0.15% (G093, G094, G155) over all other. heats prepared. In one case, on l-leat G155, a slightly.

low stress rupture ductility of 6.2% elongation was encountered. This .value is still greater than that of any obtained on control heats (no yttrium additions) or the magnesium containing heat, in spite of the fact that the test failure was within one diameter of the punch which almost always significantly reduces ductility.

There are also significant variations in rupture life illustrated by the data in Table VIII. Heats G093 and G155 containing 0.05 per cent yttrium additions displayed the highest average rupture lives of any of the other heats studied. The heat with a 0.15 per cent yttrium addition (G094) had a lower rupture life, on the average, thaneither the control heat (G081) or the 0.02 per cent yttrium containing heat (G083) but approximately equivalent to the magnesium bearing heat (G169).

TABLE VII Pressure at Time Pressure VAR Heat Addition, of Add at Four Pressure No. Amount Purity mm mm mm G080 None .023 .013 G081 None .030 .015 G083 .02 yttrium 99% .018 .018 .013 G093 .05 yttrium 99% .021 .020 .002 G094 .15 yttrium 99% .022 .025 .003 G153 None .013 .005 G155 .05 yttrium 95% .011 .011 .005 G169 .05 magnesium 75.0 75.0 150.0

TABLE VIII Heat Addition, Rupture No. Weight Percent Life Hrs. El RA G080 None 57.5 4.6 10.8 1 38.5 4.5 5.5 G081 None 317.9 4.8 4.7 174.3 4.4 8.7 G083 .02 yttrium 138.8 6.9 6.3 314.1 4.3 6.9 G093 .05 yttrium 401.1 8.7 12.9 326.5 10.4 30.6 G094 .15 yttrium 104.4 9.5 19.0 1 18.9 9.9 23.2 G153 None 24.8 3.5 12.3 26.0 4.6 8.6 G155 .05 yttrium 319.8 6.2 11.6*

220.4 15.6 29.8 G169 .05 magnesium 1 16.4 3.5 10.9

Broke within one diameter of punch mark.

The present invention has been described in detail above for purposes of illustration only and is not intended to be limited by this description or otherwise to exclude any variation or equivalent form or procedure that would be apparent from, or reasonably suggested by, the foregoing disclosure to the skill of the art.

I claim:

1. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.04% carbon, about 19% chromium, about 3.1% molybdenum, about 0.9% titanium, about 0.5% aluminum, about 18.5% iron, about 5.2% columbium, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

2. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.04% carbon, about 15.5% chromium, about 2.5% titanium, about 0.8% aluminum, about 6.8% iron, about 1.0% columbium, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

, 3. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.03% carbon, about 16% chromium, about 1.8% titanium, about 0.2% aluminum, about 41.5% nickel, about 2.9% columbium, and a balance that is essentially iron except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

4. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.05% carbon, about 12.5% chromium, about 5.7% molybdenum, about 2.8% titanium, about 0.2% aluminum, about 42.5% nickel, and a balance that is essentially iron except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

5. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.05% carbon, about 21.5% chromium, about 9.0% molybdenum, about 0.2% titanium, about 0.2% aluminum, about 2.5% iron, about 4.0% columbium, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

6. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.06% carbon, about 15% chromium, about 3.0% molybdenum, about 0.6% titanium, about 0.4% aluminum, about 7.0% iron, about 3.0% columbium, about 3.0% tungsten, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

7. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.06% carbon, about 7.0% chromium, about 16.8% molybdenum, about 2.5% iron, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

8. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.10% carbon, about 22% chromium, about 9.0% molybdenum, about 1.5% cobalt, about 18.5% iron, about 0.6% tungsten, and a balance that is essentially nickel except for an addition in said alloy yttrium in an amount ranging from about 0.02% to about 0.15%.

9. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.03% carbon, about 28% molybdenum, about 5.5% iron, about 0.4% vanadium,

ff anda' balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging fromabout 0.02% to about 0.15%.

10. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.04% carbon, about l5.5%

chromium, about 16% molybdenum, about 5.5% iron, about 3.8% tungsten, and a balance that is essentially nickel except for an additionin'said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

l l. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about.0.06% carbon, about 5.0% chromium, about 24.5% molybdenum, about 5.5%

iron, about 0.3% vanadium, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 12. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition con- 12 sisting essentially of about 0.05% carbon, about 22% chromium, about 5.0% molybdenum, about 6.0% iron, about 2.5% copper, and a balancethat is essentially nickel except for an'addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.

13. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hotworkability, said alloy having a nominal composition consisting essentially'of about 0.04% carbon, about 28% chromium, about 8.3% molybdenum, about 5.3% cop per, and a balance thatiis'essentially nickel except for an addition in said alloy'of yttriumin-an amount ranging from.ab0ut0.02% to about 0.15%.

14. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.08% carbon, about 19% chromium, about 9.8% molybdenum, about 11%. cobalt, about 3.2% titanium, about 1.5% aluminum, and a balance that is'essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%. 

1. A NICKEL BASE ALLOY OF IMPROVED CHARACTERISTICS IN AT LEAST ONE OF STRESS RUPTURE PROPERTIES AND HOT WORKABILITY, SAID ALLOY HAVING A NOMINAL COMPOSITION CONSISTING ESSENTIALLY OF ABOUT 0.04% CARBON, ABOUT 19% CHROMIUM, ABOUT 3.1% MOLYBDENUM, ABOUT 0.9% TITANIUM, ABOUT 0.5% ALUMINUM, ABOUT 18.5% IRON, ABOUT 5.2% COLUMBIUM, AND A BALANCE THAT IS ESSENTIALLY NICKEL EXCEPT FOR AN ADDITION IN SAID ALLOY OF YTTRI UM IN AN AMOUNT RANGING FROM ABOUT 0.02% TO ABOUT 0.15%.
 2. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.04% carbon, about 15.5% chromium, about 2.5% titanium, about 0.8% aluminum, about 6.8% iron, about 1.0% columbium, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 3. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.03% carbon, about 16% chromium, about 1.8% titanium, about 0.2% aluminum, about 41.5% nickel, about 2.9% columbium, and a balance that is essentially iron except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 4. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.05% carbon, about 12.5% chromium, about 5.7% molybdenum, about 2.8% titanium, about 0.2% aluminum, about 42.5% nickel, and a balance that is essentially iron except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 5. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.05% carbon, about 21.5% chromium, about 9.0% molybdenum, about 0.2% titanium, about 0.2% aluminum, about 2.5% iron, about 4.0% columbium, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 6. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.06% carbon, about 15% chromium, about 3.0% molybdenum, about 0.6% titanium, about 0.4% aluminum, about 7.0% iron, about 3.0% columbium, about 3.0% tungsten, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 7. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.06% carbon, about 7.0% chromium, about 16.8% molybdenum, about 2.5% iron, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 8. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.10% carbon, about 22% chromium, about 9.0% molybdenum, about 1.5% cobalt, about 18.5% iron, about 0.6% tungsten, and a balance that is essentially nickel except for an addition in said alloy yttrium in an amount ranging from about 0.02% to about 0.15%.
 9. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.03% carbon, about 28% molybdenum, about 5.5% iron, about 0.4% vanadium, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 10. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.04% carbon, about 15.5% chromium, about 16% molybdenum, about 5.5% iron, about 3.8% tungsten, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 11. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.06% carbon, about 5.0% chromium, about 24.5% molybdenum, about 5.5% iron, about 0.3% vanadium, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 12. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.05% carbon, about 22% chromium, about 5.0% molybdenum, about 6.0% iron, about 2.5% copper, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 13. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.04% carbon, about 28% chromium, about 8.3% molybdenum, about 5.3% copper, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%.
 14. A nickel base alloy of improved characteristics in at least one of stress rupture properties and hot workability, said alloy having a nominal composition consisting essentially of about 0.08% carbon, about 19% chromium, about 9.8% molybdenum, about 11% cobalt, about 3.2% titanium, about 1.5% aluminum, and a balance that is essentially nickel except for an addition in said alloy of yttrium in an amount ranging from about 0.02% to about 0.15%. 